The field of the invention is that of tele-communications and, more specifically, that of mobile radiocommunication networks.
More particularly, the invention relates to the switching of access nodes of a terminal in the process of implementing a plurality of applications with one or more remote communicating entities through a packet-switched network.
Initially, the terminal is connected to an origin access node but may be required to switch from the origin access node to a destination access node because of its mobility. It will be noted that the origin and destination access nodes may belong to one and the same access network or indeed to different access networks. They may be access networks of cellular mobile radio-communication networks, for example of UMTS (Universal Mobile Telecommunications System) type, or wireless, for example of WIMAX (Worldwide Interoperability for Microwave Access) type, or even wired, for example FTTH (Fiber To The Home). Whatever the case, this (these) access network(s) is (are) connected to a packet-switched network, for example an IP (Internet Protocol) type network supporting all the applications used by the terminal. Also, the terminal may be, without differentiation, a single-technology, multi-technology or reconfigurable single-technology terminal.
The access node is, for example, a base station of a UMTS, HSDPA or even LTE network (“Node B” or “Evolved node B”), or even an access point of a WIMAX network.
The multiplicity of remote communicating entities with which the terminal implements the plurality of applications may consist of one or more other user terminals and/or one or more remote servers. The packets exchanged between the terminal and the multiplicity of remote communicating entities take, for each application, a path including intermediate nodes. In the case where the terminal is switched from an origin access node to a destination access node (“handover”), the various paths taken to implement the plurality of applications are modified.
The OSI model, standardized by the ISO (International Organization for Standardization), defines data transfer management by means of seven stacked protocol layers: the physical layer (layer 1), the data link layer (layer 2), the network layer (layer 3), the transport layer (layer 4), the session layer (layer 5), the presentation layer (layer 6) and the application layer (layer 7). The various nodes of the tele-communication networks incorporate all or some of these layers. The terminal itself has all seven layers of the OSI model.
The first three layers, called bottom layers, relate to the implementation of the connection and the routing of the data. They are transparent with respect to the type of data transported. The next four layers, called top layers, are responsible for the processing of the data so that an application can be offered to the terminal.
There are other communication models that use layers, notably an IETF (Internet Engineering Task Force) model with five layers, for which the layers 5 to 7 defined above are combined.
By definition, a communication context comprises all the information required for the implementation of an application and relating to all the layers of the communication model used.
The body of communication context information required for the transport of the data with a destination communicating entity for a given application is here called transport configuration. The transport information comprises, for example, the IP address of the terminal, the identity of the access node, parameters relating to the radio link between the terminal and the access node such as the frequency.
Similarly, the body of communication context information required for the implementation by the terminal of a particular application is called application configuration. These parameters are, for example, the type of application, the bit rate, the type of coder/decoder activated for the application concerned implemented through the access node.
It will be recalled that, in the bottom layers, the protocols are exchanged between the adjacent intermediate nodes, whereas in the top layers the protocols are exchanged between the terminal and the remote communicating entity or entities which may be separated by numerous intermediate nodes. For a given application, the bottom layers are thus strung along a path between the terminal and the corresponding remote communicating entity through the intermediate nodes.
In the case of a UMTS network, the intermediate nodes are, for example, in succession, a base station controller RNC (for radio network controller), an SGSN (Serving GPRS Support Node) gateway, a GGSN (Gateway GPRS Support Node) gateway which maintain a communication context linked to the terminal and to the current applications. In the upgrades of the UMTS network, the functionalities of the controller are distributed between the base stations and the gateways which constitute the intermediate nodes, called SAE gateway and PDN gateway.
In the case of WIMAX-type wireless networks, the intermediate nodes are, for example, the AGW gateways and routers implementing the MIP protocol of the MIP (Mobile Internet Protocol) network layer.
The generic access node switching procedures comprise an access node switching decision step, a step for attaching the terminal to the destination access node by setting up a link on the data link layer, a step for determining and updating the path linking the terminal and the remote communicating entity through this new access node, and a step for reconfiguring the terminal to update the application configurations according to the state of a second link between the terminal and the destination access node.
For access node change management initialized by an element of the access network, called switching node, protocols of the “end-to-end” type are used between this switching node and the remote communicating entities for the execution of an update of the various communication contexts. The switching node is, for example, an origin access node or an intermediate node common to the various paths. The protocols are, for example, the SCTP (Stream Control Transmission Protocol) transport layer protocol, or the SIP (Session Initiation Protocol) session layer protocol. These protocols implement signaling messages whose function is to inform the destination communicating entities of a change of IP address of the terminal. For each current application, a command to execute an update of the communication context is sent to the terminal; it also includes the sending of a transport configuration change notification.
A set of notification messages is therefore sent by the switching node to the terminal corresponding to the set of current applications.
The reception by the terminal of the first notification message of the set of notification messages sent results in the reconfiguration of the terminal, notably its reconfiguration according to the modified transport configuration of the new communication context. In the case of a set of applications for which the initial transport configuration is identical, the reception of the first message results in the loss of connectivity of the terminal with the switching node. The terminal is then no longer able to receive the subsequent messages of the set of notification messages corresponding to this set of applications. In this case, additional signaling messages are necessary in order to update the paths for these pending applications. In addition to an additional resource consumption for these signaling messages, delays in updating the application configurations of the pending applications are generated which may cause these applications to crash or malfunction, notably in the case of real-time applications.
For access node switching management initialized by a switching node, there is therefore a need for access node switching capability suitable for updating a set of applications for a terminal in communication with one or more remote communicating entities.